[OpenSCAD] Difference between modelling with Openscad and Freecad

A. Craig West acraigwest at gmail.com
Wed Oct 2 09:26:25 EDT 2019

There are two use cases I can think of for being able to query objects for
information. One is when you import external objects and then wish to add
things to them. The second is to make implementing generic library code.
In the first instance, I spend a LOT of time rendering objects with shadow
cubes in various positions to determine the actual dimensions of the
imported objects. This work then has to be repeated whenever the original
object is updated to a new version. Tinkercad appears to be particularly
bad for putting objects in different positions every time...
The second instance can be worked around by adding parameters but it is
essentially redundant information. For example, a module to put a hole
through a cube could have parameters to specify the size and the
orientation of the cube, but this is essentially redundant and prone to
failure. Any time the same data needs to be specified twice, you are making
updates to the code more difficult to get right.

On Wed, 2 Oct 2019, 09:08 fred via Discuss, <discuss at lists.openscad.org>

> I am of the opinion that if one creates OpenSCAD code in a parametric
> manner, it is not necessary to query an object. By creating the object in
> this way, you've "told" OpenSCAD everything that you'd need to know later.
> cube([10, 20, 5]); definition is fine for many.
> cube([b_width, b_depth, b_height]); allows for referencing those
> assignments as often as necessary. If location is important, having
> parametric values in a translate command provides that information for
> future use.
> I learned this method from another OpenSCAD user, many moons ago, and I'm
> thankful for having been put on the right track. As I assist others in our
> makerspace, I do my best to pass along what I've learned.
> On Wednesday, October 2, 2019, 6:35:37 AM EDT, Robin2 <robin at nbleopard.com>
> wrote:
> I don't mean the user-interface, which is obviously very different between
> Openscad and Freecad. Different people like different interfaces but anyone
> could learn either or both of them if necessary.
> It seems to me there is a more fundamental difference. With Freecad (and
> other similar CAD programs) you can define an object and later "ask
> questions" about that object. For example you can select a point that is
> the
> corner of a cube and it will tell you the coordinates in 3D space. And you
> can locate the surface of a face of the cube even though it may have been
> rotated or scaled.
> However with Openscad the process of defining a model is mono-directional.
> You define the object (such as a cube) and you can have no further
> interaction with it. You cannot "ask questions".
> Is this a fair assessment, or am I completely muddled?
> As I see it very many projects can be created with an Openscad approach -
> i.e. without ever needing to be able to "ask questions". But I suspect
> there
> are some projects where the ability to easily locate a point or a surface
> of
> an existing object would be essential. And for those cases Openscad would
> not be an option.
> ...R
> --
> Sent from: http://forum.openscad.org/
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